Study On N, P And K Contents In Tissues Of Tomato And Cucumber Plug Seedlings

In view of the nutrient disorder which often occurred during the vegetable seedlings, tomato（Lycopersicon esculentum Mill.）and cucumber（Cucumis Sativus L.）seedlings was used as materialin this study to research the effects of N, P and K fertilization level on the growth and development oftomato and cucumber seedlings. To obtain the NO-3-N, P, K threshold in tissues of tomato and cucumberseedlings, NO-3-N, P, K contents were measured in different tissues of17tomato cultivars and19cucmber cultivars, the effects of N, P, K fertilization level and environmental factors on NO-3-N,P, Kcontents were also examined in two representative cultivars.1. When N supplied excess and deficiency, the seedling apparent morphological indicators suchas plant height, stem diameter, whole plant dry weight of tomato and cucumber plug seedlings weresignificantly decreased, but root/shoot ratio were increased. When P supplied inadequate and excessive,the plant height of tomato and cucumber plug seedlings were significantly decreased, but root/shootratio were increased. The effects of K inadequate and excessive supply on the apparent morphologicalindicators of tomato and cucumber seedlings were different depended on species. The chlorophyllcotents in leaves of tomato and cucumber seedlings were increased with the increased of N fertilizationlevel, reduced with decreased of P fertilization, and has little relationship with K fertllization level.Furthermore, N fertilization level has positive effects on the absorption of K, Ca and Mg. Meanwhile, Pfertilization level has negative effects on the absorption of Ca and Mg. However,as to K fertilizationlevel, species different, effects different.2. The NO-3-N, P and Kcontents varied among cultivars and tissues with significant difference.The maximal NO-3-N threshold among different tissues of a single tomato cultivar and cucumbercultivar respectively were0.79-4.42g·L-1and0.33-2.19g·L-1, the maximal P threshold respectivelywere0.116-0.704g·L-1and0.068-0.337g·L-1, the maximal K threshold respectively were2.92-6.72g·L-1and4.12-5.94g·L-1. The maximal NO-3-N threshold in a single tissue of17tomato cultivars and19cucumber cultivars respectively were2.84-4.42g·L-1and1.69-2.19g·L-1, the maximal P thresholdrespectively were0.266-0.550g·L-1and0.099-0.216g·L-1, the maximal K threshold respectively were3.23-4.93g·L-1and4.28-5.80g·L-1.3. The NO-3-N, P and K contents of tomato and cucumber plug seedlings respectively increasedas the N, P and K fertilization levels. Compared to that in the seedlings supplied with normal N, theNO-3-N content was respectively increased by at most1.86-fold and1.83-fold in the seedlings suppliedwith excessive N, while in the seedlings fertilized with low level of N, the NO-3-N content wasrepectively reduced at most97.34%and98.97%. Compared to that in the seedlings supplied withnormal P, the P content was respectively increased by at most2.41-fold and1.70-fold in the seedlingssupplied with excessive P, while in the seedlings fertilized with low level of P, the P content wasrepectively reduced at most76.21%and83.76%. Compared to that in the seedlings supplied withnormal K, the K content was respectively increased by at most1.23-fold and0.73-fold in the seedlings supplied with excessive K, while in the seedlings fertilized with low level of K, the K content wasrepectively reduced at most64.84%and40.35%. Furthermore, the NO-3-N contnent was decreasedunder when exposed to low temperature and displayed distinct changing patterns in differents tissuesand different species under other external factors. The P content was increased when fertilized withexcessive N or K and reduced when exposed to low light intensity, and displayed distinct changingpatterns in differents tissues and different species when fertilized with deficiency N or K, or exposed tolow or high temperature, or samplied at different times. The K content was increased when fertilizedwith deficiency P and reduced when fertilized with excessive P, or exposed to high temperature or lowlight intensity, and displayed distinct changing patterns in differents tissues and different species whenfertilized with excessive or deficiency N, or exposed to low temperature, or sampled at different times.4. The basic values of NO-3-N, P and K contents from17tomato cultivars and19cucumbercultivars were corrected with these environmental factors. Finally the NO-3-N threshold in tissues oftomato plug seedlings were1.75-2.72g·L-1in hypocotyls,2.07-4.04g·L-1in stems,2.18-4.83g·L-1infirst leaf petioles,0.62-1.52g·L-1in first leaves,2.31-5.10g·L-1in second leaf petioles,0.73-1.50g·L-1in second leaves,2.79-4.09g·L-1in third leaf petioles,0.40-1.53g·L-1in third leaves,2.44-4.20g·L-1infourth leaf petioles,0.40-2.13g·L-1in fourth leaves. The P threshold in tissues were0.071-0.428g·L-1in hypocotyls,0.116-0.456g·L-1in stems,0.055-0.240g·L-1in first leaf petioles,0.082-0.310g·L-1infirst leaves,0.090-0.371g·L-1in second leaf petioles,0.097-0.417g·L-1in second leaves,0.131-0.561g·L-1in third leaf petioles,0.209-0.692g·L-1in third leaves,0.310-0.586g·L-1in fourth leafpetioles,0.411-0.771g·L-1in fourth leaves.The K threshold were4.63-6.94g·L-1in hypocotyls,5.56-7.40g·L-1in stems,2.65-4.62g·L-1in first leaf petioles,2.14-4.09g·L-1in first leaves,2.80-6.93g·L-1in second leaf petioles,2.54-5.17g·L-1in second leaves,3.55-7.06g·L-1in third leaf petioles,2.69-6.24g·L-1in third leaves,4.29-7.71g·L-1in fourth leaf petioles,3.90-7.07g·L-1in fourth leaves.The NO-3-N threshold in tissues of cucumber plug seedlings were1.12-2.66g·L-1in hypocotyls,0.83-2.09g·L-1in stems,1.21-2.97g·L-1in first leaf petioles,0.22-1.03g·L-1in first leaves,0.88-2.10g·L-1in second leaf petioles,0.15-0.81g·L-1in second leaves. The P threshold were0.062-0.215g·L-1inhypocotyls,0.147-0.294g·L-1in stems,0.041-0.214g·L-1in first leaf petioles,0.136-0.296g·L-1in firstleaves,0.067-0.280g·L-1in second leaf petioles,0.241-0.420g·L-1in second leaves. The K thresholdwere3.65-6.91g·L-1in hypocotyls,4.20-7.29g·L-1in stems,3.91-5.70g·L-1in first leaf petioles,2.92-4.44g·L-1in first leaves,4.74-6.36g·L-1in second leaf petioles,3.78-5.85g·L-1in second leaves.